Hi Arnd,
thank you for taking 10 minutes to discuss this in person with me!
On Fri, Oct 20, 2017 at 12:10 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Thu, Oct 19, 2017 at 11:25 PM, Martin Blumenstingl
> <martin.blumenstingl@xxxxxxxxxxxxxx> wrote:
>>> Does dwc2 also use separate nodes for the roothub? From your
>>> description it sounds like it would not be affected by your patch.
>> currently it doesn't use separate notes for the roothub - however,
>> with this patch it could (although I haven't explicitly tested this)
>
> Ok.
>
>>> Since you used a dtb that already listed an endpoint device below
>>> an xhci, that would answer my earlier question of whether it worked
>>> before your patch series, and you tested that it still works with your
>>> patches applied and the roothub node added in the dtb. Now we
>>> just need to make sure we don't break existing dtb files that don't
>>> have the roothub node but do have endpoint device nodes.
>> the endpoint you're seeing is the root-hub - you can see the full .dts here: [0]
>>
>> maybe my patch description or documentation is not clear - could you
>> please explain what makes you think that specifying the root-hub
>> didn't work before (so I can update the comments where needed)?
>> to sum up what this series does: find the node with reg = <0>; (= the
>> root-hub) and get all PHY instances from the child-nodes
>> this should not change any existing behavior except if someone had a
>> node with reg = <0>; below any USB controller node (which was
>> undocumented behavior before my patches)
>
> Maybe I misunderstand what the actual change to the hierarchy
> is. Quoting from your example for the new code
>
> + &usb1 {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + roothub@0 {
> + compatible = "usb1d6b,3", "usb1d6b,2";
> + #address-cells = <1>;
> + #size-cells = <0>;
> + reg = <0>;
> +
> + port@1 {
> + reg = <1>;
> + phys = <&usb2_phy1>, <&usb3_phy1>;
> + phy-names = "usb2-phy", "usb3-phy";
> + };
>
> The way I understand it, an endpoing device would now be
> located in
>
> &usb1/roothub@0/port@1/hub@2/device@1
>
> where previously it was in
>
> &usb1/port@1/hub@2/device@1
>
> Is that correct?
this is not how it's currently implemented - let's find out if this is
a misunderstanding on my side
the second example is still valid with this series, while the first
example won't work with the code as it is
> I don't see any code that can deal with both cases and still
> assign the correct of_node pointer to the device device@1 in
> the end (maybe it's there and you just need to point me
> to the right patch).
it's not you - that code is (currently) not there
> The reason why we have to be careful here is that the
> Linux device hierarchy is not just derived from DT here, but
> it gets created from the physical devices under &usb1
> and the 'struct device' hierarchy has to match the DT hierarchy
> exactly.
yes, I fully agree with you here
I will post an updated version of this series which includes an
updated usb-xhci dt-binding documentation to show how the end result
(after this series) can look like. I'll include Rob in the loop again
so we don't introduce a broken binding.
Regards,
Martin
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